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Ethereum upgrade on hold: Glamsterdam's Hoodi test halted

Ethereum developers postponed Glamsterdam on the Hoodi testnet after a gas-pricing security review. We explain the flaw, who must act and what comes next.

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Ethereum's core developers have postponed Glamsterdam on the Hoodi testnet, the last public rehearsal before a mainnet date. The Ethereum Foundation said the pause gives time to study how one gas-pricing proposal, EIP-8037, behaves with contracts already live on mainnet. This article looks at why a change to gas accounting can alter code nobody edits, and what node operators now have to do.

The change in one paragraph

Glamsterdam was due to activate on Hoodi at epoch 132,352, at 17:42:48 UTC on October 26, 2026. According to the Ethereum Foundation, developers agreed on the ACDE #248 call to delay it, and no replacement date has been set. Unchained reported that the test was called off four days before its planned start. Christine D. Kim of research firm Protocol Watch wrote on X on Oct. 22 that security problems found by the firm ChainSecurity were the cause. Glamsterdam would enshrine proposer-builder separation (EIP-7732) and introduce block-level access lists (EIP-7928). It already ran on the Sepolia testnet from Oct. 6.

Under the hood: how a gas rule can change old code

Every Ethereum operation costs gas, a unit of computing work, and creating or reading state each has its own price. ChainSecurity's Oct. 13 analysis, as described by Unchained, examined a pair of Glamsterdam proposals that reprice gas for creating and accessing state: EIP-8037 together with EIP-8038.

Many smart contracts make quiet assumptions about gas. A contract may pass a limited amount of gas into an inner call, then check whether that call succeeded. If the price of the work inside the call changes, the same call can take a different path, even though the bytecode on chain is identical.

That is the risk ChainSecurity described. In its words: "Even with unchanged contract code, a failure path that previously reverted can now complete". The difference matters. A revert undoes the whole transaction, so the user can simply try again. A failure path that completes instead records the outcome on chain. According to Unchained, the firm warned this can turn an action that could be retried into a failure that is permanent.

  • Before: a failing inner call reverts, the state is untouched, and the user retries.
  • After repricing: the same call may finish down its failure branch and commit that result.
  • Why it is easy to miss: the contract code itself does not change, only the price of the work it triggers.
  • What the Foundation wants to study: how EIP-8037 interacts with contracts already deployed on mainnet.

This is why the review is framed around mainnet contracts, not the testnet. A testnet run mainly shows whether clients agree with each other. How contracts already live on mainnet react to new gas prices is a separate question, and it is the one the Foundation said it wants time to study.

Who is affected

The people who must act are Hoodi node and validator operators. The Ethereum Foundation said they should update both their execution and consensus clients, and that validators must update both the beacon node and the validator client. The releases to use are those whose notes confirm the October 26 activation has been removed. The Foundation also warned that client versions listed in its earlier Hoodi announcement should not be assumed to include the postponement.

Kim gave operators two routes on X: go back to an older release without the fork scheduled, or wait for an execution client update that drops it. Unchained noted a practical trap. Besu developers merged a pull request on Oct. 22 that unschedules Amsterdam on Hoodi, but a node still running Besu 26.10.0 will activate the fork anyway until it runs a release containing that change.

For everyone else, the Foundation was explicit: the notice sets no mainnet date, and Ethereum mainnet users and ETH holders need to take no action.

What was rolled back, and what was not

The postponement removes two scheduled activations: Amsterdam on the execution layer and Gloas on the consensus layer. It also cancels a planned rise in the Hoodi block gas ceiling, which was set to reach 200M at that epoch too. Barnabas Busa, who handles DevOps at the Ethereum Foundation, removed the fork from Hoodi's shared configuration files, returning them to how they looked before it was scheduled, Unchained reported.

The Foundation stressed one limit. This rolls back settings for a future upgrade. It does not rewind Hoodi's chain history, so blocks already produced stay as they are.

When is the Ethereum upgrade date now?

There is no confirmed date. According to Unchained, the agenda of the Oct. 22 call had listed Dec. 1, Dec. 8 or Dec. 9 as possible mainnet dates, with a choice planned for the following week if Hoodi went smoothly. With the Hoodi run cancelled, that choice has no confirmed date.

Before the Oct. 22 call, security researcher pcaversaccio had opened a GitHub discussion urging developers to weigh the findings, though he said the call belonged to others. The next signal to watch is a new Hoodi activation in client release notes.

Sources

AI wrote this summary from the primary documents and reports cited above. It went live automatically after checks that figures match those sources and nothing is copied; there was no human review. It explains a protocol or rule change and is not investment advice.

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